Breast cancer outcome has improved significantly over the last 10 years. However, an important number of patients still relapse, while others receive unnecessary therapy as we are unable to distinguish whether patients have low-risk or high-risk disease. Breast cancer behavior is regulated, in part, by the PI3K/PTEN/AKT signaling pathway, which interact bidirectionally with hormone receptors and further interacts at multiple levels, creating a complex signaling network. My hypothesis is that breast cancer tumors can be classified by changes in protein signaling in the PI3K/PTEN/AKT pathway and that tumor response to specific therapeutic regimens can be predicted and improved by identifying and targeting this pathway. My specific aims are: (1) To classify breast cancers by characterizing the functional proteomic expression/activation signature of the PI3K/PTEN/AKT signal transduction cascade, (2) To determine whether the proposed functional proteomics-based classification reflects response to preoperative taxane (paclitaxel or docetaxel) and 5-fluoruracil, doxorubicin/epirrubicin, and cyclophosphamide (paclitaxel-FA/EC) chemotherapy, and (3) To determine whether a therapeutic intervention targeting the PI3K/PTEN/AKT pathway in combination with chemotherapy is an effective treatment for triple receptor (ER, PR, and HER2)- negative locally advanced breast cancer (LABC). We will perform reverse-phase protein microarray analysis (RPPA) of 90 frozen preoperative breast cancer samples and analyze the PI3K/PTEN/AKT cascade. The data will be used as a training set to define a breast cancer signaling profile associated with response to preoperative chemotherapy. We will obtain a validation set of 50 samples and apply the proteomic profile to determine its specificity and sensitivity in predicting response to therapy. We will develop a phase II randomized clinical trial in women with triple receptor-negative LABC in which patients will be treated with either standard chemotherapy (docetaxel followed by FEC) or docetaxel plus RAD001 followed by FEC. This study will reveal whether the addition of an mTOR inhibitor to standard neoadjuvant chemotherapy in patients with triple receptor-negative breast cancer causes molecular changes (inhibition/activation) in the PI3K/PTEN/AKT pathway and the clinical effects of this intervention. This study will lead to a better understanding of the mechanisms underlying the wide variation in breast cancer behavior and therapy responsiveness and will also identify other therapeutic targets in patients for whom conventional therapy is inadequate. At the same time it will provide me with the experience, knowledge, and skills necessary to launch and conduct an independent translational research career in breast oncology. The outcome of this project is expected to position me to submit a competitive R01 application during the fourth year of the proposed award.